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Implementing and Maintaining an ISP Backbone. Kevin Butler. Tier 1 ISP Backbones. Comprise some of the world’s largest IP networks Tier 1 companies include Sprint, AT&T, PSINet

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tier 1 isp backbones
Tier 1 ISP Backbones
  • Comprise some of the world’s largest IP networks
  • Tier 1 companies include Sprint, AT&T, PSINet
  • UUNET has the world’s largest IP data network, presence on four continents and future expansion into Latin and South America
service level agreements
Service Level Agreements
  • SLAs are an important and prestigious tool in attracting and maintaining customers
  • Comprised of uptime guarantees and bounds on latency through various geographic regions
  • most ISPs currently have latency < 50ms across the US
supporting the customer
Supporting the Customer
  • Quality and expertise of first-line customer support varies wildly between companies
  • depending on size, geographic location and company focus, some front-line support teams outsourced to third parties
  • some in-house high level support teams have skills equivalent or superior to NOCs
network operations centres
Network Operations Centres
  • Generally the teams concerned with backbone maintenance and support
  • trend towards consolidation into “Super-NOCs” (eg. one for Americas, one for Europe)
  • specialisation within NOC for product support (eg. dial, VPN, backbone NOCs)
noc tools
NOC Tools
  • NOCOL - Network Operations Centre On Line (freeware UNIX)
  • Mediahouse monitoring (mainly web)
  • Micromuse Netcool (now owned by Lucent) - used by MCI WorldCom, PSINet, BT
dial access
Dial Access
  • Dial is a major selling point, especially with customers who travel a lot or are their own ISPs
  • connections made through an Ascend MAX TNT, which can support up to 720 concurrent callers
  • back-end is a DS-3 into a backbone router, routers advertised by an IGP (eg. RIP)
dial related technologies
Dial-Related Technologies
  • COBRA (Central Office Based Remote Access) allow building of virtual POPs by backhauling PRIs
  • RADIUS (Remote Authentication Dial In User Service)
integrated services digital network
Integrated Services Digital Network
  • ISDN customers authenticate by RADIUS similar to dial users
  • underlying architecture similar but dial equipment often administrated differently
  • ISDN maintained within same AS as backbone whereas dial often in its own AS
ds 1 and high speed access
DS-1 and high-speed access
  • Customer connections usually multiplexed, come into DSU as a channelised DS-3
  • gateway routers on ISP side usually Cisco 7500 series, increasingly using Cisco 12000
  • customers connect using Cisco 1604, 2621, some 3600 series, very large customers use 7500 series routers
gateway routers
Gateway Routers
  • obtain routes from customers usually statically, but sometimes by BGP
  • usually run link-state IGP within AS (eg. OSPF, IS-IS)
  • Cisco 7513 backplanes 1.8 Gbps while 12008 does 40 Gbps
where does traffic go from here
Where does traffic go from here?
  • Most ISPs have two levels of networks above the access router
  • Metropolitan networks aggregate gateway traffic, generally city-wide (if multiple POPs in city)
  • transit networks aggregate metro network’s traffic, responsible for inter-city transport
atm switches
ATM Switches
  • Terminate long-haul OC-12, OC-48 circuits and metro rings
  • Choice of vendor contingent on ISP, commonly Newbridge, Fore Systems (ASX-1000 and ASX-4000)
example of an atm interface
Example of an ATM interface

TR1.EG1:

interface ATM2/0

description To HA13.BLAH1 3C1

atm vc-per-vp 512

atm pvc 16 0 16 ilmi

!

interface ATM2/0.195 point-to-point

description To XR1.BLAH1 ATM6/0

ip address 146.188.200.98 255.255.255.252

ip router isis Net-Backbone

atm pvc 195 0 195 aal5snap

clns router isis Net-Backbone

implementation of bgp
Implementation of BGP
  • BGP run between autonomous systems and peers, as well as multi-homed customers
  • monolithic AS broken up into BGP confederations for ease of work
  • routes controlled using access lists and route maps
slide19
BGP
  • Communities are destinations that share common attributes (eg. through access-list filters)

BGP table version is 23718690, local router ID is 205.150.242.2

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

*>i24.64.0.0/19 198.133.49.7 100 0 6327 6172 i

*>i24.64.0.0/14 198.133.49.7 100 0 6327 i

*>i24.64.32.0/19 198.133.49.7 100 0 6327 6172 i

*>i24.64.64.0/19 198.133.49.7 100 0 6327 6172 i

*>i24.64.96.0/19 198.133.49.7 100 0 6327 6172 i

*>i24.64.192.0/19 198.133.49.7 100 0 6327 6172 i

*>i24.64.224.0/19 198.133.49.7 100 0 6327 6172 i

*>i24.65.0.0/19 198.133.49.7 100 0 6327 6172 i

*>i24.65.96.0/19 198.133.49.7 100 0 6327 6172 i

*>i24.65.128.0/19 198.133.49.7 100 0 6327 6172 i

advantages of bgp for user
Advantages of BGP for User
  • Allows for load-sharing and redundancy
  • routes can be biased through AS path prepending
  • requirement is high-quality router with close to 100% uptime to avoid connection flaps and subsequent route dampening
common customer issues
Common Customer Issues
  • Static routes on backbone - often difficult to spot, can cause very strange routing results
  • pull-up routes for netblocks smaller than /24, required to avoid BGP dampening
  • BGP recalculations - if done on a transit router, entire backbone segments can experience outages
customer requirements of the backbone
Customer Requirements of the Backbone
  • Redundancy - networks are redundant but card failures can take down whole routers
  • physical connection to POP from customer is SPF
  • low latency - massive increases in demand on backbone makes this difficult
  • over $2 million a day spent on global backbone upgrades
dsl low cost high speed
DSL: low cost, high speed
  • DSL might phase out ISDN connections
  • difficult to troubleshoot from network standpoint
  • connections pass through telco’s frame or ATM cloud between DSLAM and VR
  • RedBack SMS (Subscriber Management System) 1000 commonly used as VR
redback sms 1000
RedBack SMS 1000
  • Supports up to 4000 sessions
  • OC-3 out to metro network
  • traffic-shaping accomplished with profiles

atm profile samplecust

counters

shaping vbr-nrt pcr 1000 cdvt 100 scr 100 bt 10

increasing capacity
Increasing Capacity
  • Backbone capacity increasing at a huge rate
  • Traffic engineering combined with high backplane becoming increasingly important
  • many ISPs turning to Juniper routers
  • UUNET rolled out production OC-192c with Juniper M160 running MPLS
juniper routers
Juniper Routers
  • JUNOS supports MPLS and RSVP

isis {

interface all;

}

ospf {

area 0.0.0.0 {

interface so-0/0/0 {

metric 15;

retransmit-interval 10;

hello-interval 5;

}

}

}

[edit]

distributed dos attacks
Distributed DOS attacks
  • Can be very detrimental to backbone (even causing switch crashes)
  • Combated by rate-limiting ICMP on routers
  • Most effective defense is community-wide egress filtering; requires co-operation throughout the Internet
canadian network challenges
Canadian Network Challenges
  • Geographically, population resides in virtually a straight line across the south
  • major focus is on southbound capacity to the US
  • CRTC regulations on telcos create different arrangements
  • heterogeneous network to the US, integration a big issue
questions
Questions?
  • Anything I can clarify or expand on...
  • Thank you!
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